Title:Constraints of the compactness of the isolated neutron stars via X-ray phase-resolved spectroscopy

Abstract: A model with a condensed iron surface and partially ionized hydrogen-thin
atmosphere allows us to fit simultaneously the observed general spectral shape
and the broad absorption feature (observed at 0.3 keV) in different spin phases
of the isolated neutron star RBS 1223. We constrain some physical properties of
the X-ray emitting areas, i.e. the temperatures (Tpole1 ~ 105eV, Tpole2 ~99eV),
magnetic field strengths Bpole1 ~ Bpole2 ~ 8.6x10^13G) at the poles, and their
distribution parameters (a1 ~ 0.61, a2 ~ 0.29, indicating an absence of strong
toroidal magnetic field component). In addition, we are able to place some
constraints on the geometry of the emerging X-ray emission and the
gravitational redshift (z ~0.16+0.03-0.01) of the isolated neutron star RBS
1223.